What HP engine do I need for river cruising?

[magnetman]

18 minutes ago, Jonny P said:

1hp was estimated as the continuous rating of a horse but in short bursts a horse can achieve something like 15hp.

 

 

 

yes and also horses vary. 

 

one of my sister's horses was just 14H3 (below 14H2 is when its a pony)

 He was a dressage horse. Half pass and all that. Walking sideways etc. Very nice. 

 

He would not have been good at hauling heavy vessels or carts. We did have a cart pony as well. 

 

Barge haulage horses are massively stronger than Sam the dressage horse but they are still both called horses. 

 

 

 

 

17 minutes ago, Tonka said:

Isn't the rated horsepower of an engine over rated. I remember my father in law used to talk about true horsepower of an engine. He used to say that a 1500 cc engine had a true horsepower of 15 and a 3000 cc engine had a true horsepower of 30. Which when I think of my 3100 cc BD3 compared to our previous 1500 cc BMC makes a lot of sense, yet if you look at the rated horsepower the BMC is higher

Wasn't he talking about the torque. 

 

 

Torque (ft-lbs) = (HPx5252)/RPM 

 

So the BMC 30HP@3000pm = 52.52 ft-lbs.

 

Beta BD3 35HP@1,400rpm = 131.3 ft-lbs.

 

Bolinders "Pup" 9hp semi Diesel 9hp @ 375rpm. 126 ft-lbs torque. 

Edited February 27 by magnetman

[cheesegas]

6 minutes ago, Tonka said:

Isn't the rated horsepower of an engine over rated. I remember my father in law used to talk about true horsepower of an engine. He used to say that a 1500 cc engine had a true horsepower of 15 and a 3000 cc engine had a true horsepower of 30. Which when I think of my 3100 cc BD3 compared to our previous 1500 cc BMC makes a lot of sense, yet if you look at the rated horsepower the BMC is higher

Rated SAE horsepower is horsepower - there's no 'true' or 'false' about it, unless the manufacturer is outright lying, which I doubt a big company like Leyland would do.

 

However, if you have a small displacement BMC and a large displacement BD3 both rated at the same horsepower, the BMC will need to spin faster to achieve the same output. Horsepower = torque (ft/lb) x RPM divided by 5252.

 

Due to the noise and prop pitching, a BMC won't ever be set up to do 3000rpm in a narrowboat, so it'll never be able to output its full 30hp. However, as the BD3 doesn't need to spin as fast, it's possible to set it up so it can achieve Beta's rated output.

 

Looking at those two specific engines however, the Beta BD3 is basically a derated Ford/New Holland BSD333 tractor engine which is simply run slower to achieve the derating.

 

The BSD333 is a 3 litre lump rated at 60hp @ 2500rpm, vastly more powerful than a 1.5 litre BMC at 30hp @ 3000rpm. Makes sense given how it's a whole litre bigger. However, in a boat, the BD3 won't ever run at 2500rpm as it's marketed as a low-speed, traditional-ish engine; like I mentioned above, less RPM = less power. I expect Beta may set the governor so it can't ever rev as high as Ford intended it to.

 

It feels more powerful simply because it's a bigger, more powerful engine spinning slowly.

[magnetman]

Just now, cheesegas said:

I expect Beta may set the governor so it can't ever rev as high as Ford intended it to.

 

Yes they did do this and had some problems particularly with exhaust smoke. 

 

They set it with too low an idle compared with the manufacturers specification. 

[David Mack]

33 minutes ago, Tonka said:

Isn't the rated horsepower of an engine over rated. I remember my father in law used to talk about true horsepower of an engine. He used to say that a 1500 cc engine had a true horsepower of 15 and a 3000 cc engine had a true horsepower of 30. Which when I think of my 3100 cc BD3 compared to our previous 1500 cc BMC makes a lot of sense, yet if you look at the rated horsepower the BMC is higher

Was your father in law referring to the RAC or Tax horsepower of an engine? This was a power rating calculated from the cylinder diameter and number of cylinders in the early days of motoring, and used to determine vehicle tax. Originally a fairly accurate measure, but as engine efficiencies improved it underestimated the actual power. And by not taking the stroke length into account it encouraged the development of long stroke engines which would be lower tax rated.

https://en.m.wikipedia.org/wiki/Horsepower#RAC_horsepower_(taxable_horsepower)

 

[booke23]

1 hour ago, blackrose said:

Turning against a decent current on a river?

 

You don't say....With no tow path for a horse either! And with CRT generally not permitting horse drawn operations! 

 

Very obviously I'm not suggesting he gets a horse. I (and others in the past) mention the 'hp cliché' to illustrate the point that a lot of hp is not necessary. 

 

But we do need to know what size boat it is to give an accurate answer. 

[David Mack]

5 minutes ago, booke23 said:

But we do need to know what size boat it is to give an accurate answer. 

Whatever answer the forum can give it will not be accurate. There's too many unknowns.

[Bee]

Not quite as straightforward as it seems. The purpose of the engine is to turn the prop, the prop is what gives the boat the shove it needs. Big old engines turned a big slow prop, modern higher speed engines turn a smaller prop a bit faster (roughly speaking) There are complex calculations for all of this and many, many variables that clever people have done but a correctly propped boat with a BMC 1.5 will be fine, basically if you see a boat you like have a run in it and if it gets along OK with a bit in reserve then it is OK (Oh and some boats are just slow because of their shape and will always be that way no matter what engine you put in it.)

[booke23]

12 minutes ago, David Mack said:

There's too many unknowns.

 

That's why we've been asking for more details from the OP. 

[magnetman]

Also is the OP looking at buying a Boat with an engine in it 

 

(edit as yes this in the OP)

Edited February 27 by magnetman

[Tonka]

32 minutes ago, David Mack said:

Was your father in law referring to the RAC or Tax horsepower of an engine? This was a power rating calculated from the cylinder diameter and number of cylinders in the early days of motoring, and used to determine vehicle tax. Originally a fairly accurate measure, but as engine efficiencies improved it underestimated the actual power. And by not taking the stroke length into account it encouraged the development of long stroke engines which would be lower tax rated.

https://en.m.wikipedia.org/wiki/Horsepower#RAC_horsepower_(taxable_horsepower)

 

That could be the answer

[Wafi]

1 hour ago, Jonny P said:

1hp was originally estimated to be the continuous rating of a horse but in short bursts a horse can achieve something like 15hp.

 

Given that one horse could pull two fully laden canal boats for 18 hours a day every day and a modern leisure at boat at the same kind of speed is perhaps outputting 5hp it does seem that equating one horse to 1hp for canal work is an underestimate.

Another important difference is that an actual horse would be standing on the bank.

 

To simplify the comparison, imagine 2 boats travelling upstream against a 4 knot current; one has a conventional inboard engine, the other is being pulled by a tractor. If they're just stemming the current, the engine on the boat is already working reasonably hard, whereas the engine on the tractor is doing no work at all, in fact it doesn't even have to be running. At 5 knots, both engines are applying the same forward force to the boat, but the one on the tractor is having a much easier time because it's only moving forward at 1 knot over the ground. Indeed, because power is the product of force and speed, the engine on the boat needs to produce 5 times as much useful power as the engine in the tractor because it's travelling 5 times as fast, relative to the thing it's pushing against.

[MrsM]

17 hours ago, IanD said:

There's also the question for river use -- especially with older BMC engines which may have small skin tanks -- of whether the engine and cooling system can sustain full power for what could be several hours going upstream against a current 

Indeed, I would want to know that skin tank size would be adequate for a boat that is working hard punching against the current on a river. Our boat was 40bhp and when the Trent was quite lively we made very slow progress going against. 

[Alan de Enfield]

53 minutes ago, David Mack said:

Was your father in law referring to the RAC or Tax horsepower of an engine? This was a power rating calculated from the cylinder diameter and number of cylinders in the early days of motoring, and used to determine vehicle tax. Originally a fairly accurate measure, but as engine efficiencies improved it underestimated the actual power. And by not taking the stroke length into account it encouraged the development of long stroke engines which would be lower tax rated.

https://en.m.wikipedia.org/wiki/Horsepower#RAC_horsepower_(taxable_horsepower)

 

 

 

 

I still have my petrol ration book from 1973 issued but never actually needed.

The ration depended on the HP of your vehicle mine is "20HP and over", or by engine size "2201 CC or over"

 

I cannot remember which car I had at that time - it was either a 3.3 litre Vauxhall Cresta, or a V6 Ford Zodiac

 

[IanD]

1 hour ago, cheesegas said:

Rated SAE horsepower is horsepower - there's no 'true' or 'false' about it, unless the manufacturer is outright lying, which I doubt a big company like Leyland would do.

 

However, if you have a small displacement BMC and a large displacement BD3 both rated at the same horsepower, the BMC will need to spin faster to achieve the same output. Horsepower = torque (ft/lb) x RPM divided by 5252.

 

Due to the noise and prop pitching, a BMC won't ever be set up to do 3000rpm in a narrowboat, so it'll never be able to output its full 30hp. However, as the BD3 doesn't need to spin as fast, it's possible to set it up so it can achieve Beta's rated output.

 

Looking at those two specific engines however, the Beta BD3 is basically a derated Ford/New Holland BSD333 tractor engine which is simply run slower to achieve the derating.

 

The BSD333 is a 3 litre lump rated at 60hp @ 2500rpm, vastly more powerful than a 1.5 litre BMC at 30hp @ 3000rpm. Makes sense given how it's a whole litre bigger. However, in a boat, the BD3 won't ever run at 2500rpm as it's marketed as a low-speed, traditional-ish engine; like I mentioned above, less RPM = less power. I expect Beta may set the governor so it can't ever rev as high as Ford intended it to.

 

It feels more powerful simply because it's a bigger, more powerful engine spinning slowly.

Exactly what I was saying.

 

Most narrowboats with "modern" (I use this advisedly for BMC...) high-speed diesels around 30hp-40hp have installations done on the cheap -- no hospital silencer or Aquadrive or sound insulation -- and as a result make the boat rattle and the steerer go deaf at anywhere close to maximum rpm.

 

On top of this the engine runs at power levels far below the optimum (best efficiency is usually around the peak torque point) when cruising on canals, and even more so when used for battery charging. "Usable" power -- for longer periods on rivers, not short emergency bursts -- is only around half the rated power.

 

Instead of this (e.g. Beta 43, 4-cyl 2000cc, 240kg, 43hp at 2800rpm, 2:1 gearbox, 18" x 12" prop) a far better solution would be to use a smaller engine -- something like a Beta 25 (3-cyl 900cc, 110kg, 25hp at 3600rpm, with a 3:1 gearbox and 18" x 12" prop) -- with good silencing and sound insulation.

 

Even though it's running 50% faster at a given power level (e.g. cruising) it would probably make less noise and vibration to start with (less than half the capacity) and be easier to install (smaller, less than half the weight). It would also use less fuel when cruising and even more so when battery charging.

 

And it would be cheaper, the difference in engine cost would more than make up for the extra cost for sound/vibration-proofing. The only disadvantage is you can't fit big/dual alternators for fast battery charging, though some other engine ranges (Barrus Shire?) do allow this on smaller engines.

 

Unfortunately none of the builders seem to have thought this through, so they all choose the same engine sizes as everybody else does (and the engine suppliers recommend)... 😞 

Edited February 27 by IanD

[magnetman]

7 minutes ago, IanD said:

Exactly what I was saying.

 

Most narrowboats with "modern" (I use this advisedly for BMC...) high-speed diesels around 30hp-40hp have installations done on the cheap -- no hospital silencer or Aquadrive or sound insulation -- and as a result make the boat rattle and the steerer go deaf at anywhere close to maximum rpm. On top of this the engine runs at power levels far below the optimum (best efficiency is usually around the peak torque point) when cruising on canals, and even more so when used for battery charging. "Usable" power -- for longer periods on rivers, not short emergency bursts -- is only around half the rated power.

 

Instead of this (e.g. Beta 43, 4-cyl 2000cc, 240kg, 43hp at 2800rpm, 2:1 gearbox, 18" x 12" prop) a far better solution would be to use a smaller engine -- something like a Beta 25 (3-cyl 900cc, 110kg, 25hp at 3600rpm, with a 3:1 gearbox and 18" x 12" prop) -- with good silencing and sound insulation. Even though it's running 50% faster at a given power level (e.g. cruising) it would probably make less noise and vibration to start with (less than half the capacity) and be easier to install (smaller, less than half the weight). It would also use less fuel when cruising and even more so when battery charging. And it would be cheaper, the difference in engine cost would more than make up for the extra cost for sound/vibration-proofing. The only disadvantage is you can't fit big/dual alternators for fast battery charging, though some other engine range do allow this on smaller engines.

 

Unfortunately none of the builders seem to have thought this through, so they all choose the same engine sizes as everybody else does (and the engine suppliers recommend)... 😞 

 

It could be a psychological effect. 

 

A similar phenomenon with cars. 

 

people are driving around in cars which sometimes have engines capable of producing several hundred horsepower. 

 

Entirely unnecessary but very common. 

 

There is some sort of cognitive bias making people think that more powerful must be better. 

 

 

[MtB]

9 minutes ago, Alan de Enfield said:

 

I cannot remember which car I had at that time - it was either a 3.3 litre Vauxhall Cresta, or a V6 Ford Zodiac

 

 

My dear old departed Dad drove a Ford Zodiac when I was a brat. I'm 100% sure it was a straight six not a V6. Did the change this to V6 in the later models perhaps? Bizzard will remember! 

 

Three litres I think, but not so certain about that. It was so quiet it was difficult to hear if the engine was running or not when stationary. 

[magnetman]

 

Its probably related to the animal brain which is erroneously saying 'If you can go faster quicker you can escape from the predator and thereby increase the chances of survival'. 

 

This is why people in cars sometimes race each other 'I am going to get to my destination faster than you are going to get to your destination and thus I am demonstrating an increased probability of survival' 

 

Animal brain gone mad. 

 

 

[Alan de Enfield]

Just now, MtB said:

 

 

My dear old departed Dad drove a Ford Zodiac when I was a brat. I'm 100% sure it was a straight six not a V6. Did the change this to V6 in the later models perhaps? Bizzard will remember! 

 

Three litres I think, but not so certain about that. It was so quiet it was difficult to hear if the engine was running or not when stationary. 

 

 

It was a long time ago but I think the Ford was a V6 around 2.8 - 3 litre, and the Vauxhall was a 'straight 6'

 

 

A quick google :

 

Ford started to work on the MKIV Zephyr/Zodiac in 1961. It insisted on getting new technologies on the car, such as the rear independent suspension, an alternator instead of a dynamo, and even a cigarette lighter. Even though the Zodiac was the upmarket model, it was offered in two trim levels, with the Executive being the full-options one.

Under the hood, Ford dropped a 3.0-liter V6 engine paired to a three-speed automatic gearbox. A no-cost option for a four-speed manual transmission was offered.

[IanD]

11 minutes ago, Alan de Enfield said:

 

It was a long time ago but I think the Ford was a V6 around 2.8 - 3 litre, and the Vauxhall was a 'straight 6'

 

A quick google :

 

Ford started to work on the MKIV Zephyr/Zodiac in 1961. It insisted on getting new technologies on the car, such as the rear independent suspension, an alternator instead of a dynamo, and even a cigarette lighter. Even though the Zodiac was the upmarket model, it was offered in two trim levels, with the Executive being the full-options one.

Under the hood, Ford dropped a 3.0-liter V6 engine paired to a three-speed automatic gearbox. A no-cost option for a four-speed manual transmission was offered.

 

Depending on dates this might have been the Zodiac Mk III -- the "Z-cars" one from the '60s -- not the boxy rectangular Mk IV. A friend had an old battered Mk III in the early 80s which had a straight-six (2.5l) and a hideously unpredictable column gearchange, capable of dealing out random prizes in the gear lottery... 😉 

[Jonny P]

45 minutes ago, Wafi said:

Another important difference is that an actual horse would be standing on the bank.

 

To simplify the comparison, imagine 2 boats travelling upstream against a 4 knot current; one has a conventional inboard engine, the other is being pulled by a tractor. If they're just stemming the current, the engine on the boat is already working reasonably hard, whereas the engine on the tractor is doing no work at all, in fact it doesn't even have to be running. At 5 knots, both engines are applying the same forward force to the boat, but the one on the tractor is having a much easier time because it's only moving forward at 1 knot over the ground. Indeed, because power is the product of force and speed, the engine on the boat needs to produce 5 times as much useful power as the engine in the tractor because it's travelling 5 times as fast, relative to the thing it's pushing against.

No.

 

Unless the brakes were engaged the engine in the tractor would most definitely have to be doing some work to hold a boat still against a 4 knot current.

 

You're overthinking it. To move the same boat the same distance through the same piece of water at the same speed requires equal power. Doesn’t matter how it is achieved.

Edited February 27 by Jonny P

[IanD]

27 minutes ago, Jonny P said:

No.

 

Unless the brakes were engaged the engine in the tractor would most definitely have to be doing some work to hold a boat still against a 4 knot current.

 

You're overthinking it. To move the same boat the same distance through the same piece of water at the same speed requires equal power. Doesn’t matter how it is achieved.

 

Not really, since providing static force doesn't mean any work is done, a rope can do the same, or torque on a wheel.

 

The only reason the engine is producing power is the the clutch is slipping; at the output (wheels) you have torque*zero rpm which is no power, at the engine you have torque*rpm which is power, all of which ends up as heat in the clutch -- which will probably burn out pretty quickly as a result.

 

Heat is work and work is heat, as Flanders and Swann told us... 😉 

 

You're right that moving a boat at a given speed *relative to the water* consumes power, but this is still proportional to boat speed -- if the water is at 5kts and the boat is stationary then a given force is needed (like torque above) but no power from a tractor, I can tie the boat up with a rope which consumes no power because the boat isn't going anywhere.

 

If the power comes from the propeller then that's different, even though the boat isn't moving the boat engine needs the same power as using a tractor to pull the boat at 5kts though still water.

 

If you work out the equations, it turns out that a boat has minimum fuel use per mile if it travels upstream at half the speed of the current... 🙂 

Edited February 27 by IanD

[magnetman]

Land based haulage will use less power as there are no propeller losses. 

 

 

[IanD]

6 minutes ago, magnetman said:

Land based haulage will use less power as there are no propeller losses. 

 

 

True, but the real reason -- if there's a current -- is nothing to do with propeller losses, it's that you're pulling against the fixed land not the moving water. This would be true even if the propeller was 100% efficient.

 

Propeller losses make this worse, but this is a smaller effect. If you take the best-case I quoted above -- for example, going upstream at 2.5 kts (7.5kts through the water) against a 5kt current, a boat engine with even a perfect propeller would need 3x the power of a tractor (because power is force x speed). A real propeller (60% efficiency?) would increase this to 5x...

Edited February 27 by IanD

[Jonny P]

15 minutes ago, IanD said:

 

Not really, since providing static force doesn't mean any work is done, a rope can do the same, or torque on a wheel.

 

The only reason the engine is producing power is the the clutch is slipping; at the output (wheels) you have torque*zero rpm which is no power, at the engine you have torque*rpm which is power, all of which ends up as heat in the clutch -- which will probably burn out pretty quickly as a result.

 

Heat is work and work is heat, as Flanders and Swann told us... 😉 

 

You're right that moving a boat at a given speed *relative to the water* consumes power, but this is still proportional to boat speed -- if the water is at 5kts and the boat is stationary then a given force is needed (like torque above) but no power from a tractor, I can tie the boat up with a rope which consumes no power because the boat isn't going anywhere.

 

If the power comes from the propeller then that's different, even though the boat isn't moving the boat engine needs the same power as using a tractor to pull the boat at 5kts though still water.

 

If you work out the equations, it turns out that a boat has minimum fuel use per mile if it travels upstream at half the speed of the current... 🙂 

I nearly changed the word work given that if the boat is stationary no useful work is being done. But it’s the word that feels right in everyday usage though.

 

It still holds that when towed the adverse force applied by the current has to be overcome. It seemed to me the post I responded to meant you got that bit for free when towing.

 

13 minutes ago, magnetman said:

Land based haulage will use less power as there are no propeller losses. 

 

 

 

There are losses in any system - in the transmission, in the slipping of the horses hooves - but ultimately the work is done by the force applied to the water by the propeller or by the tow rope on the mast and that’s the point at which effective power needs to be considered.

Edited February 27 by Jonny P

[bizzard]

T'would need more power goin uphill than downhill.